Transformer



Oct. 24, 1933. E. STElNERT 1,932,051

TRANSFORMER Filed Aug. 20, 1932 @an i @5572.

f MJ Emil slag/'nerf @ie/] BY a: i.

ATTORNEY PATENT OFFICE 1,932,051` 'raaNsFonMEa Emil Steinert, Sharon, Pa., assignor to Westing-` house Electric & Manufacturing Company, East Pittsburgh, Pa., aeorporatlon of Penn- Sylvania Application August zo, 1932. serial 9 claims. (ci. 17545;)

Myinvention relates to transformers and more particularly to means for improving the current path between the windings.

ratio and the phase-angle performance of current transformers. 1

In current transformers, particularly those of the higher voltage ratings, the arrangement of the primary and secondary windings is such as to give a high magnetic leakage fluxbetween them because of the relativ ly short effective length of the high-low space or flux leakage A portion ofthe leakage flux that passes between the primary and secondary windings traversesl the outer leg of the iron core, that'is, the portion of the core that is remote from that portion about which` the primary and secondary windings are positioned.

The leakage ilux which traverses this portion ofA the iron core adds, vectorially, with the secondary or useful iiux, therebyincreasing the flux density 1 in the outer leg of the coreand increasing the exciting current required. 1 1

The presence of both the lleakage and the secondary flux in a-lar'ge part of the iron core requires that this. portion of thev magnetic circuit f operate at a higher point on the saturation curve than the remaining portion of the core. requires vmore primary ampere Yturns to excite the iron and consequently leaves less to be reproduced l in the secondary than would be the case if the whoe core carried the secondary uxonly. i I propose lo eliminate most `of the leakage ilux from the iron core by providing a third winding known las the equalizer winding, positioned aboutthe outer-leg of the transformer and con'- nected with either the secondary winding or a portion thereof, or with an auxiliary winding surrounding that portion of the magnetic `core about which the secondary winding is positioned. It is an object of my invention toprovide a transformer having a substantially constant ratio of current transformation `with varying primary 1 circuit current.

1 ing specification describing a preferred embodi-r which carries the iiux 4m. Besides this a similar It is another object of my invention to provide a transformer of Vthe class described with simple means for adjusting the phase-angle relation be'- tween ihe primary and secondary current to a desired value.

A further object of my invention is to provide a transformer of the class described in which the I dimensions of the iron circuit and the relating parts may be relatively small.

Other objects will be apparent from ihe followment of my invention. 1

In the drawing, Figure 1 is a view, partly in longitudinal cross-section and partly in side elevation, of a transformer, the several parts of which are organized in accordance with my invention.

1 Fig. 2 is an end elevational view of the transformer shown in Fis. 1.

Thisv Fig. 3 is a vector diagram showing the 'phaseangle relation between a number of the quantities affecting the operation of the transformer; and

Fig. 4 illustrates curves showing approximately the difference in phase-angle relations and in the ratio of current transformation in a transformer of the character described when the equalizing coils of the invention are employed.

Referring to the drawing, and particularly Figs. l and 2 thereof, 1 indicates a core or loop of magnetic material shown as being rectangular in form. A. secondary winding 2 and a primary winding 3 are shown positioned about the upper horizontal-V portion, or winding leg, of the core. An equalizer coil 4 is shown wound about the` vlower horizontal portion, or'cuter leg, of 4the transformer core and connected' with a coil 5, which has a different numberof turns than the core 4, and is wound about the winding leg within the opening of the" primary winding 2. The connection between coil -4 and coil 5 is such that. if the two coils had the same r`number of turns and the secondary ilux alone were in the core, the voltages induced in the two coils would buck each other, and no current `would flow.

Instantaneous directions of currents and of magnetic nux are indicated in Fig. l. and the approximate phase-relation between the several quantities are shown in the vector diagram of vReferring to Figs. 1 and 3, that portion of the leakage ux which traverses the iron core is represented by r., and the useful secondary flux is represented by os. Thev dotted line in Fig. 3 indicates the ilux'inthe outer leg of the transformer when theequalizer winding is not employed. rpt indicates the flux in this leg when the equalizer winding is employed. The vector oi. that connects the ends of the vectors o, and represents the value of im. when the equalizer winding 4 is not employed. ,f l

4u. is limited by the Vcurrent which flows in the equalizer circuit, andis just large enough to induce the voltage needed to circulate said current.

The primary must supply, in .addition to the ampere turns which appear in the secondary, other ampere turns to magnetize the core. When the equalizer is used, the magnetizing ampere turns are represented by the two small full-line `triangles at the extreme right of. Fig. 3. The first triangle consists of magnetizing ampere-turns 1 parallel to y43s and non-disc ampere-turns perpendicular to 4m. These excite the 1peut of the core ioo los

miy

to e ite the core are much less when the equaliser in use.

The voltage induced in the equaliser coil 4 by the iiux n is represented on the vector diagram oi'l'ig. 8 by the line est. A value of em is assumed sumcient to overcome the impedance of the equaliser windings. The voltage induced in the auxthe du'x e. is indicated on the diagrambythelineee.. Thecurrentinthecircuitottheequaliser windingiiisassumedtobe in phase with the resultant induced voltage es.

Itwillbenotedthatachangeinthenumberof By a suitable selection ot the number of turns i coils 4 and t. the angle betweenthe vector 19N,

andtheeatensionofvectorlimcanbemadevery .zamall. or even reduced to aero. I'he resulting ohmgeinthelengthofthevectorLNtmaybe compensatediorbychlngingthenumberofturns Nt in secondary winding,` thus maintaining .g current L.

1empare-turns approaches unity.

. above description refersto an auxiliarywindingseparatefromthesscondarywind- `lng cllthe transformer, it 'will be noted that the 4 may be connected to all or a t ofthesecondarywindingwhichwllliunctienes an iiqualiser winding of the transformer.

fl. A transformer having winding associated with the `ioopofvinagneticinaterial,aprimiiryandasecvinding ondary wound about a portion of said core.` and means for reducing the strmv ilux which enters said magnetic path comprisingI windings electrically connected together and inductively t related to diiIerent portions of said magnetic core on opposite aides of the location cut by stray ilux paling primaryand secondary windings.

a primary winding ahptedtobeconnectedinseries relationwith aiinewhosecurrentistobe measured. a secondarywindinginductivelyrelatedtosaidprimary windmg, a core o! magnetic material associated wtthsaidwindingscomprisingawindinglegand an outer leg, and means for maintaining the ratio eicurrenttramfcrmationattheterminalsorthe sundingsmbstantially constant for varying loads comprising equaliser windings on said windim legandonsaidouterleg.

i td transformer having a primary winding 1,9ss,osi

adapted to be interposed in series relation with a line whose current is to be measured. a secondary winding inductively related to said primary winding, and a core of magnetic material associated with said windings comprising a winding leg and an outer leg, and means for neutralizing the ei.'- fect of stray nux in said outer core leg comprising a winding on said outer leg connected with a winding on the winding leg.

5. A transformer having a primary winding adapted to be interposed in series relation with a line whose current is to be measured, a secondary winding inductively related to said primary wmding. a core comprising a loop of magnetic material one portion of which passes through said windings. and means for maintaining the ratio of current transformation substantially constant for varying loads comprising an equalizer winding about a `portion of said core remote from the primary and secondary windings and connected with winding turns about a portion of the core surrounded by said'windings.

6. In a rmer, a core structure comprising a closed loop of magnetic material having a winding leg, asecondary winding wound about a primary winding wound about said secondary winding. and means for compensating for variations in the ratio ci current transformation for varying loads comprising an equalizer winding about that portion of said core opposite said winding leg and connected with winding' turns placed about said winding leg.

7. A transformer having a primary winding adapted to be connected in series relation with a circuit whose current is to be measured, a secondary winding inductively related to said primary winding, a core of' magnetic material associated with said windings comprising a winding leg and an outer leg. and means for -maintaining the phase angle relation between the current in the primary and secondary windings substantially constant for varying loads comprising equalizer lwindings on said winding leg and on said outer 8. A transformer having a primary winding adapted to be interposed in series relation with a circuit whose `current is to be measured. a secondary winding inductively related to said primary winding. a core comprising a loop o1' magnetic material one portion of which passes through said windings. and means for minimizing the phase angle displacement between the currents in said primary and secondary windings comprising an equalizer winding about a portion of said core remote from the primary and secondary windings and connected with winding `turns about the portion of the core surrounded by said primary and secondary windings.

9. In a transformer, a core structure comprising a closed loop of magnetic material having a winding leg. the secondary winding wound about said a primary winding wound about said secondary winding, and means for compensating for phase angle error between the currents in said primary and secondary windings for varying loads comprising an equalizer winding wound about that portion oi the core opposite said winding leg and connected with winding turns positioned about said winding leg.

EMIL STEINERT. 

